Engines such as diesel engines emit particulates contained in exhaust gases, and are associated with a particulate trap disposed in their exhaust gas passage for entrapping the emitted particulates. As the amount of particulates trapped by the particulate trap is increased, the resistance to the flow of exhaust gases through the particulate trap is also increased, and the power output of the engine is lowered. To prevent such a flow resistance increase and an engine power output drop, these engines are also combined with an emission purifier for burning the particulates entrapped by the particulate trap.
The emission purifier burns the trapped particulates with the combustion gases emitted from a burner, or with the heat from an electric heater and supplied air.
Where the electric heater is employed, since the electric heater is energized by a battery on the automobile equipped with the engine, the sufficient amount of electric energy may not be available, for burning the particulates completely in restoring the particulate trap.